1. Field of the Invention
The present invention relates to a temperature controlling apparatus, and more particularly, to an apparatus and method for sensing defects of a temperature sensor that is used in an apparatus for controlling temperature, by sensing a change of specific resistance of the temperature sensor.
2. Description of the Related Art
In general, a semiconductor device is fabricated by performing various processes, and during performance of such various processes, various kinds of chemicals are used. Processes using chemicals are mainly performed by using a bath which stores the chemical solution. Semiconductor fabricating processes that use such a bath may include etching processes for removing an unnecessary film or cleaning processes for a wafer. Such cleaning and etching processes generally utilize an overflow system in which the processes are performed by overflowing pure water and chemicals in the bath.
In a wet/clean station that includes wet equipment using such chemicals, first and second baths are provided for cleaning, and a QDR (Quick Drop Rinse) bath and a final bath are also included. During a cleaning process or a wet etching process using chemicals in such baths as described, temperature appropriate for the chemical processes should be uniformly maintained, to gain a desired process effect. That is, since a relation between temperature and an etching rate depends on characteristics of the chemicals, the etching rate changes according to an increase or a decrease in temperature, to thus result in overetching or underetching and poor product quality.
A chemical temperature controlling apparatus for addressing such problems is disclosed in Korean Opened Patent Publication No. 1998-066186. In Korean Opened Patent Publication No. 1998-066186, a value of the normal temperature is periodically measured, and a determination temperature is changed according to the measured value, so as to maintain temperature of a semiconductor fabricating process equipment at the changed determination temperature value and control it as an optimum process condition temperature.
Such a temperature controlling apparatus as noted above senses a change of resistance of the temperature sensor indicative of highness and lowness of temperature. In other words, when current temperature is lower than a determination value, electrical power is supplied to a heater to drive the heater, and when the current temperature is higher than the determination value, electrical power to the heater is cut off to maintain constant temperature. Such temperature controlling apparatus turns the heater power on/off according to temperature detected by the temperature sensor. A state in which the heater becomes powered-on is a normal operation, and a state in which the heater is powered-off and cooled is an inverse operation, whereby current (I)=voltage(V)/resistance(R) in accordance with Ohms law, such that resistance and current inversely operate. Therefore, in the case of an inverse operation, the resistance of the temperature sensor increases as shown in FIG. 1A and current then decreases, so that temperature of the semiconductor fabrication process is controlled to decrease. In the case of a normal operation, when the resistance of the temperature sensor decreases as shown in FIG. 1B and current then increases, temperature of the semiconductor fabrication process is controlled to increase.
Accordingly, when a temperature sensor is corroded and thereby disconnected, or when the specific resistance of the temperature sensor increases, the detected temperature by the temperature sensor becomes higher than the actual temperature. In other words, in a case of a 3.8 Ω increase in specific resistance, the detected temperature of the chemical bath is increased by 10° C. Even if the determined temperature is controlled under a state that the actual temperature becomes heightened due to an increase of the specific resistance of the temperature sensor, a temperature of the solution of chemical bath does not reach temperature determined actually. Further, when the temperature sensor is corroded and thereby shorts, or if the specific resistance is reduced, the detected temperature by the temperature sensor becomes lower than the actual temperature. Even if the determined temperature is controlled under such a state that the actual temperature becomes low, a temperature of solution of the chemical bath becomes higher than the actually determined temperature. Therefore, despite that the temperature of the solution of the chemical bath is higher or lower than the actually determined temperature, it is recognized that the solution has reached the determined temperature, to thus cause a defect in the semiconductor fabricating process.